1. Field of the Invention
The present invention particularly relates to a compound eye image pickup apparatus including an array of a plurality of optical systems.
2. Description of the Related Art
A “compound eye” image pickup apparatus has been conventionally known that includes an optical system whose small size is achieved by dividing the optical system into a plurality of optical systems. This “compound eye” has structure of an insect's eye and has a configuration in which, for example, the optical system includes a lens array of a plurality of lens units. The optical system can be downsized by downsizing a diameter of each lens unit and a focal length thereof.
However, it is difficult to provide this compound eye image pickup apparatus with an optical zoom function for varying an image capturing field angle. This is because an optical zoom function that varies the image capturing field angle by moving a lens included in the optical system requires a mechanical move mechanism, which leads to an increase in the size of an image pickup system. To deal with this problem, for example, Japanese Patent Laid-open No. 2005-20718 discloses a configuration in which a short-focus lens unit and a long-focus lens unit that have different field angles are arranged to capture an image including the same part of an object. Specifically, a zoom image obtained by an image pickup element for a long-focus lens is inset in part of a wide image obtained by an image pickup element for a short-focus lens, thereby obtaining an image having a high resolution in the part and a low resolution and a wide field angle in the other part. The configuration includes a single image pickup element and a plurality of optical systems, thereby achieving a thin and small multifocus image pickup device.
Japanese Patent Laid-open No. 2003-283907 discloses a compound eye image pickup apparatus that adds signals of the same part of an object imaged on an image pickup element so as to achieve a high S/N ratio while having an improved resolution with a small pixel size.
However, in the configuration of Japanese Patent Laid-open No. 2005-20718, imaging optical systems have different focal lengths and different focal planes, and thus no imaging optical systems share the same optical property. Thus, signals of the same part of the imaged object cannot be added to improve the S/N ratio, and a sufficient image quality of a reconfigured output image cannot be obtained.
On the other hand, the compound eye image pickup apparatus disclosed in Japanese Patent Laid-open No. 2003-283907 can add signals of the same part of the object and signals of the vicinity thereof that are obtained from each image pickup unit, thereby improving the S/N ratio. However, imaging optical systems arranged in the apparatus have an identical focal length, which results in a degraded resolution of an output image of a field angle different from the field angle of the imaging optical systems.